Theory of Atomic Structure and Processes

原子结构和过程理论

• 批准号: RGPIN-2016-04494
• 负责人: Drake, Gordon
• 金额: $ 3.64万
• 依托单位: University of Windsor
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=649575
• 关键词: Theory; Atomic; Structure; Processes

The unifying theme of this proposal is the development of new measurement tools through the combined application of both high***precision theory and experiment to atoms. In brief, the theoretical side rests on a foundation of our essentially exact nonrelativistic***wave functions for atoms such as helium and lithium, combined with the state-of-the-art for relativistic and quantum electrodynamic***effects. A comparison with experiment then provides a window into new physical phenomena. A prime example from the past grant period***is the use of the isotope shift in atomic transition frequencies to deduce the size and shape of exotic "halo" nuclei such as helium-6***and helium-8. This work at the interface between atomic and nuclear physics is done in collaboration with the top experimental groups***in the world at high energy particle accelerators such as Argonne (U.S.), GSI (Germany) and TRIUMF (Canada). The accelerator-based***projects are subjected to rigorous standards of feasibility and significance before being approved.***Future work will build on our past experience and extend it in several directions. First, the isotope shift method developed by***us is now well recognized as the most accurate method, and in many cases the only method available, to measure the size of***halo nuclei. These exotic structures have extra planetary neutrons surrounding a tightly bound core of neutrons and protons. The***significance of the results is that they enable one to distinguish among the various theoretical models proposed for the effective***forces holding the nucleus together. By studying structures that fall apart easily, we learn about the forces holding them together.***Our previous work on the halo nuclei of helium, lithium and beryllium will next be extended to boron, in collaboration with experimental groups at GSI, Germany. Fascinating trends are emerging across the periodic table of isotopes.***Second, we are opening up a new area of study with applications to search for new physics beyond the standard model of elementary***particle physics. When a halo nucleus decays via the weak interaction, it emits both a beta-particle (high energy electron) and a neutrino. The standard model predicts the angle between the two outgoing particles, and any deviation from it would signal new physics beyond the standard model. We are currently calculating the recoil contribution due to the atomic electrons that must be taken into account in interpreting the measurements. Our preliminary results indicate that there is a serious disagreement with a landmark 1963 experiment. There is an urgent need for both new experimental work and further calculations that take into account the atomic electrons that are "shaken off" following the beta decay process. This work is an ongoing collaboration with an experimental group at the University of Washington.***Other proposed work focuses on fundamental tests of atomic theory and quantum electrodynamics.**

这项建议的统一主题是通过将高精度理论和实验结合应用于原子来开发新的测量工具。简而言之，理论方面的基础是我们对氦和锂等原子的基本精确的非相对论性波函数，以及相对论性和量子电动力学效应的最新研究成果。然后，与实验的比较为新的物理现象提供了一个窗口。在过去的资助期 *** 中，一个主要的例子是利用原子跃迁频率中的同位素位移来推断奇异的“晕”核的大小和形状，如氦-6 *** 和氦-8。这项在原子物理和核物理之间的界面上的工作是与世界上顶级的实验组 * 在高能粒子加速器上合作完成的，如阿贡（美国），GSI（德国）和TRIUMF（加拿大）。以加速器为基础的 * 项目在获得批准之前必须遵守严格的可行性和重要性标准。今后的工作将以我们过去的经验为基础，并在若干方面加以推广。首先，我们发展的同位素位移方法现在被公认为是测量晕核大小的最精确的方法，在许多情况下也是唯一可用的方法。这些奇特的结构有额外的行星中子围绕着一个紧密结合的中子和质子核心。结果的 * 意义在于，它们使人们能够区分为将原子核固定在一起的有效 * 力提出的各种理论模型。通过研究那些容易破裂的结构，我们可以了解将它们连接在一起的力量。我们以前对氦、锂和铍的晕核的工作将与德国GSI的实验组合作，下一步扩展到硼。同位素周期表中出现了快速的趋势。第二，我们正在开辟一个新的研究领域，应用于寻找超越基本粒子物理学标准模型的新物理。当晕核通过弱相互作用衰变时，它会发射出一个β粒子（高能电子）和一个中微子。标准模型预测了两个出射粒子之间的角度，任何偏离都将标志着标准模型之外的新物理。我们目前正在计算反冲的贡献，由于原子电子，必须考虑到在解释测量。我们的初步结果表明，这与1963年的一个具有里程碑意义的实验存在严重分歧。 目前迫切需要新的实验工作和进一步的计算，考虑到原子电子是“摆脱”后的β衰变过程。这项工作是与华盛顿大学的一个实验小组正在进行的合作。其他拟议的工作集中在原子理论和量子电动力学的基本测试。